Clinical/methodical issue: Magnet resonance imaging (MRI) is an excellent anatomical reference method for the combination with positron emission tomography (PET). But MRI does not produce data, which can be directly used for attenuation correction of PET data, potentially compromising quantitative accuracy of PET.
Standard radiological methods: Hybrid-positron emission tomography/computed tomography (PET/CT) is an established standard diagnostic tool, particularly for staging and restaging in oncology. Attenuation correction of PET data is performed with a µMAP derived from low-dose-CT, considered as a robust method.
Methodical innovations: Using standardized MRI-sequences, tissue classes are segmented and attenuation maps are obtained, based on empirical density values. In addition, new reconstruction algorithms and the possibility to acquire PET and MRI simultaneously with MRI-based motion correction are available. These advances have improved image quality and quantitative accuracy of the PET-data in PET/MRI.
Performance: In numerous oncological studies PET/CT and PET/MR were rated as equal in their diagnostic performance. The combination of functional-metabolic PET and multiparametric MRI with excellent soft tissue contrast complement each other with regard to their diagnostic information in numerous tumor entities.
Practical recommendations: The standard diagnostic workup for lung cancer is currently still based on PET/CT. In numerous tumor entities, the combination of PET/MRI can provide additional diagnostic information.
Keywords: Attenuation correction; Cross-sectional imaging; Motion correction; Radiation exposure; Tumor diagnosis.